Considering the metre and structure, at least, I'd suggest it's been made "in the style of" Thomas Campbell, Glasgow poet, best known in his own day for "The Pleasures of Hope", a long didactic poem. Among his shorter pieces is "The Exile of Erin". I should think this possible influence - not overlooking the native tradition, naturally - has been suggested before and elsewhere.

By the way, the Wild Geese was indeed the term for those Jacobites who left Ireland "after Aughrim's great disaster" to take service in Continental armies, principally that of France. Nevertheless, following this exodus from the last decade of the seventeenth century, the tradition of the Irish winning battles for everyone except themselves continued throughout the eighteenth, with the Irish Brigade gaining great distinction (with the inevitable losses, too) at Ramillies and Fontenoy. Among the "Irish Legion" of Napoleon's army - two infantry regiments - were some followers of Emmet who had been rescued from their British captors en route to their being transported as slaves. Finally, Napoleon's habitual green tunic, with red collar and cuffs, was the "petit tenue" of a cavalry regiment, Les Chasseurs a Cheval de la Garde Imperiale.